Script that converts TRK to TCK using https://github.com/MarcCote/nibabel/tree/streamlines_tck

trk2tck.py

import os
import argparse
import nibabel as nib


def build_argparser():
    DESCRIPTION = "Convert tractograms (TRK -> TCK)."
    p = argparse.ArgumentParser(description=DESCRIPTION)
    p.add_argument('tractograms', metavar='bundle', nargs="+", help='list of tractograms.')
    p.add_argument('-f', '--force', action="store_true", help='overwrite existing output files.')
    return p


def main():
    parser = build_argparser()
    args = parser.parse_args()
    for tractogram in args.tractograms:
        if nib.streamlines.detect_format(tractogram) is not nib.streamlines.TrkFile:
            print("Skipping non TRK file: '{}'".format(tractogram))
            continue

        output_filename = tractogram[:-4] + '.tck'
        if os.path.isfile(output_filename) and not args.force:
            print("Skipping existing file: '{}'. Use -f to overwrite.".format(output_filename))
            continue

        trk = nib.streamlines.load(tractogram)
        nib.streamlines.save(trk.tractogram, output_filename)

if __name__ == '__main__':
    main()

thanks for this! works perfectly, and very useful (i needed to get my .trk files into .tck so i could use mrtrix's tracks2prob)